This invention relates to fuel systems for the internal combustion engines of automobiles or similar vehicles. and more particularly relates to fuel systems of the type which attempt to achieve increased operating efficiency and/or reduced exhaust-pollution, from the engines serviced thereby, by heating of the fuel conducted to such engines.
Prior patents disclosing fuel systems of the aforesaid general type, which incorporate fuel heating means therein, include the following: U.S. Pat. Nos. 3,807,377, 3,780,714, 3,797,468, 3,472,214, 3,286,703, 2,974,656, 2,748,758 and 2,179,235.
If a fuel system of the type in question is to operate in a safe and satisfatory manner, the heated fuel (usually gasoline) delivered thereby to the engine serviced by the system must be maintained within a relatively limited temperature range. The optimum fuel temperature will vary in accordance with the characteristics of the engine, carburator and the like of the particular automobile or similar vehicle in association with which the fuel system is employed. Therefore, while a fuel system incorporating a non-adjustable fuel heater may perform satisfactorily in one particular vehicle, the performance of the same fuel system in another vehicle may be totally inadequate and even detrimental or dangerous. It is also important, even in connection with a fuel system adapted for use in only one particular vehicle, that the heat output of the fuel heater be automatically regulated and varied in such a manner as to maintain the heated fuel at its optimum temperature irrespective of changes in the operating conditions of the vehicle. In the absence of adequate automatic regulation of the heat output of the fuel heater, a fuel system which performs satisfactorily when the vehicle is cruising will likely severely overheat the fuel when such vehicle is coasting or is stationary. Conversely, a system which performs satisfactorily when the vehicle is coasting or stationary will inadequately heat the fuel delivered to the carburator when the vehicle is cruising unless at such time the heat output of the fuel heater is increased to accommodate the increased fuel flow. The same problem, -- i.e., that of the fuel entering the carburator being at a temperature less than the desired optimum one -- will also arise if the fuel is heated to only its ultimate optimum temperature at the heater and is then allowed to undergo significant cooling during its thereafter ensuing passage from the heater to the carburator. Detection and regulation of the temperature of the fuel are for the most part meaningless functions unless the desired end-result, which is maintenance of an optimum fuel-temperature at a location closely adjacent the carburator of the system, is realized thereby.
Another major problem that has heretofore been encountered is that of "vapor lock" of the fuel pump components of fuel systems incorporating fuel heaters. Such problem is a serious one since as long as a "vapor lock" condition persists, the vehicle is virtually useless. Whatever benefits it might otherwise possess or yield, therefore, a fuel system which is subject to "vapor lock" of its fuel pump is not satisfactory and will not enjoy public acceptance.
A fuel system of the type in question should also be economical to manufacture, install and maintain. From the installation viewpoint, it is highly desirable that the system be readily installable within not only new vehicles, but also within existing vehicles of the many different makes and models presently in use. This requires that the system be capable of utilizing, with little and preferably no modifications thereto, the existing carburator, fuel pump and other major fuel-handling components of the vehicle at hand. It also requires that the fuel heater component of the system be of a sufficiently compact size and versatile design as to be mountable and usable in whatever location and limited space as might be available in the engine comparts of different vehicles.
Lastly, a system of the type in question should for reasons of safety be of a durable "closed" construction not susceptible to fuel leakage and not requiring the accumulation of large quantities of fuel within any components located inside of the engine compartment of a vehicle.